KVM: Remove duplicated declaration of kvm_vcpu_kick

There are two declarations of kvm_vcpu_kick() in kvm_host.h where
one of them is redundant. Remove to keep the git grep a bit cleaner.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>